This section provides background information related to the present disclosure which is not necessarily prior art.
Organic light-emitting diode (OLED) display is gaining popularity due to a number of advantages. An OLED display device usually comprises: an anode layer, functional film layers, and a cathode layer, etc., wherein the functional film layers may include: a hole transmission layer, an organic light emitting layer, and an electronic transmission layer. Film forming methods of the organic light emitting layer may include: an evaporation coating film forming method, molecular beam epitaxy, an organic chemical vapor deposition method and sol-gel process, etc. The evaporation coating film forming method has the advantages of simple operation and easiness to control film thickness, and has become a major method of forming functional film layers like organic light emitting layer.
A film formed by the evaporation coating film forming method are called an evaporation coating film, and different thickness of the evaporation coating film will cause different luminous intensity of the OLED display device, thus affecting the display effect and service life of the OLED display device. The evaporation coating film forming method usually forms an evaporation coating film by an evaporation apparatus. Schematically, FIG. 1 shows a structural schematic view of an evaporation apparatus 00 provided by related art. As shown, the evaporation apparatus 00 comprises: an evaporation coating chamber 001, an evaporation source 002 disposed in the evaporation coating chamber 001, a thickness detector 003 disposed on an inner wall of the evaporation coating chamber 001 and above the evaporation source 002, a switch 004 disposed in the evaporation coating chamber 001 and above the thickness detector 003, a substrate supporting rack 005 disposed in the evaporation coating chamber 001 for supporting a substrate A to be coated, a mask board supporting rack 006 disposed in the evaporation coating chamber 001 for supporting a mask board B, and a motor 007 disposed external to the evaporation coating chamber 001. The motor 007 is connected to the substrate supporting rack 005 and the mask board supporting rack 006 respectively through a transmission shaft 008 penetrating through the chamber wall of the evaporation coating chamber 001, wherein the evaporation source 002 may be a point evaporation source, and the mask board B is disposed at the side of the substrate A to be coated facing the evaporation source 002. When the evaporation apparatus 00 is used to form an evaporation coating film, the evaporation source 002 is heated to make the evaporation source 002 evaporate gaseous molecules of the evaporation coating material, and the deposition rate of the molecules of the evaporation coating material can be detected by the film thickness detector 003; when the deposition rate of the molecules of the evaporation coating material reaches a target rate, the switch 004 and motor 007 are turned on, and the motor 007 brings the substrate supporting rack 005 and the mask board supporting rack 006 to rotate through the transmission shaft 008, so as to make the substrate A to be coated and the mask board B to rotate, and the molecules of the evaporation coating material are evaporated and deposited onto the substrate A to be coated to form an evaporation film through the mask board B.
The inventor has found out that the related art at least has the following problem: limited by the structures of the dot evaporation source and the substrate, the deposition rate of the molecules of the evaporation coating material is different at different positions of the substrate, and the formed evaporation coating film is prone to have the phenomenon of being thick near the center and being thin near the periphery, and thus the uniformity of the thickness of the evaporation coating film is poor.